We have used a forced consumption technique where drug solutions are the only drinking fluid available, an operant drinking technique where food-deprived animals are rewarded with food for drug drinking and the schedule-induced polydipsia technique with drugs in the drinking fluid to induce rats to consume drugs. We plan to use these three techniques to induce animals to drink a variety of drugs including opioids, CNS stimulants, major and minor tranquilizers, antidepressants, sedative-hypnotics and hallucinogens. With the continued use of these techniques we can study tolerance development and the development of drug dependence (both physical and behavioral dependence). The success of these techniques in inducing high daily drug intakes over long time periods will allow us to study behavioral changes, particularly changes in operant behavior, in these animals during the development of tolerance and drug dependence, as well as during drug withdrawal. Finally, our capacity to induce chronic ingestion of drugs at high doses while measuring behavior, will provide us with an excellent baseline against which to evaluate acute drug interaction when drugs are injected into animals chronically ingesting drug solutions. BIBLIOGRAPHIC REFERENCES: McMillan, D. E. and Leander, J. D. Schedule-induced oral self-administration of etonitazene. Pharmacol. Biochem. Behav. 4:137-141 (1976). McMillan, D. E., Leander, J. D., Wilson, T. W., Wallace, S. C., Fix, T., Redding, S. and Turk, R. T. Oral ingestion of narcotic analgesics by rats. J. Pharmacol. Exp. Therap. 196:269-279 (1976).